1. Field of the Invention
The applicant is knowledgeable of the design and operation of pulverizing mills used to grind mineral samples into a fine powder. The pulverizing mill together with many other types of machines require an orbital or vibratory motion in order to work. These machines include for example screens for screening particles, cone crushers for crushing rocks, and shakers and stirrers for shaking and stirring laboratory solutions, biological/medical products and specifications, and the like.
The invention relates to an electric machine operable as a motor to provide motion required to drive a pulverizing mill but which can alternatively be operated as a generator to provide electricity or an electrical load.
2. Description of the Related Art
Traditionally, the orbital or vibratory motion required on such machines is imparted to an object by attaching the object to a spring mounted platform to which is coupled an eccentrically weighted shaft driven by a motor; or, via bearings to an eccentric shaft driven by a motor. A mechanical coupling such as a gear box, belt, or universal joint is used to couple the output of the motor to the shaft.
However, the very motion that these machines are designed to produce also leads to their inevitable and frequent failure. Specifically, the required orbital or vibratory motion leads to fatigue failure in various components of the machines including mechanical couplings, transmissions, bearings, framework and mounts. The cost of repairing such failures is very high. In addition to the cost of repairing the broken component(s) substantial losses can be incurred due to down time in a larger process in which the failed machine performs one or more steps. A further limitation of such machines is that they produce fixed orbits or motions with no means of dynamic control (i.e. no means of varying orbit path while machine is running).
The present invention has evolved from the perceived need to be able to generate orbital or vibratory motion without the limitations and deficiencies of the above described prior art.
It is also well known in the art that an electric machine can operate as a motor when driven by electricity to provide a mechanical output such as a rotation of a shaft and, can operate as an electricity generator or electrical load when a mechanical input is provided such as a rotation of a shaft by crank, water wheel, or similar means.
According to the present invention there is provided an electric machine having a magnet producing lines of magnetic flux extending through an air gap in a first direction. The air gap is formed by oppositely disposed magnetic poles. A support capable of at least two-dimensional motion relative to the magnet in a single plane contains the support. The support is provided with at least two electrically conductive paths, each having a current carrying segment which extends with a circumferential aspect relative to a center of the support, and the segments are disposed in and extend across the lines of magnetic flux within the air gap in a second direction substantially perpendicular to the first direction. Thus, interaction of an electric current flowing through a particular segment and the lines of magnetic flux produces a thrust force to cause motion of the support relative to the magnet.
Preferably, the support is made of an electrically conductive material and is provided with a plurality of apertures disposed inboard of an outer peripheral edge of the support wherein at least one of the electrically conductive paths is constituted by the portions of the support that extend about the apertures. Also, preferably, the support is in the form of a wheel having a central portion hub with spokes extending radially outwardly from the central portion hub and an outer rim joining the spokes, respectively. Each aperture is thus defined in the wheel by the space formed between adjacent spokes and sectors of the central portion of the hub and rim. Each conductive path comprises two pairs of adjacent spokes and respective sectors of the central portion of the hub and rim extending between the two spokes.
In another aspect, the electric machine further includes an induction device for inducing an electric current to flow through the electrically conductive paths. Preferably, the induction device is supported separately from the support. Also, preferably, the induction device comprises a plurality of transformers, each having a primary coil and a core about which the primary coil winds. The core of each transformer interlinks with adjacent apertures so that an electric current flow in the primary coil of a transformer can induce an electric current to flow through the electrically conductive paths about the corresponding adjacent apertures.
In one embodiment, the induction device includes a transformer having a core formed into a closed loop and provided with a plurality of windows through which respective spokes of the support pass, each window bound by opposed branches of the core that extend in the same plane as the support and opposed pairs of legs of the core that extend in a plane perpendicular to the support. Also, with a plurality of primary coils, a primary coil wound about at least one of the branches of the core of each window. Thus, in use, when an alternating current is caused to flow through the primary coils, lines of magnetic flux are created that circulate about the windows in the core, the majority of the flux being shared in legs of the core between adjacent windows so that the lines of magnetic flux circulating about a particular window induce a current to flow through the spoke passing through that window and the conductive paths containing that spoke.
The number of segments can be equal to the number of electric phases supplied to the support. Also, preferably, the magnet is shaped as a closed loop magnet and provides a common polarity flux in the air gap. The device can include a coupling for mechanically coupling the support to a mechanical input that moves the support two-dimensionally in the single plane to induce an electric current to flow in the conductive paths. Thus, the machine can operate as an electric generator.